Abstract: The annual biomasses of trunk, branch and leaf of Populus gansuensis (Populus nigra var. italica×P. siminii), as a single tree and population, have been calculated by analogy simulation and average treemodular standard tree method respectively in this paper. The growth analysis of this tree species have also been carried out by classical method. The results are as follows:(1) By calculating the existed biomass, the percentage of trunk, branch, and leaf to the overground part of a tree(S₁%, B₁%, L₁%), tended to be stable from the 8th year, which is 77%, 18% and 5% respectively.(2) Based on the dry matter accumulated over 16 years, the percentage of leaf to the overground part of the tree amounted to 21.5%, and it would raise with the increase in age.(3) The leaf area ratio (LAR) of both an individual tree and a population trended to decrease during the investigation. The net assimilation rate (NAR) and the relative growth rate (RGR) tended to fall from the 8th year.(4) The leaf area index (LAI) of a population shot up with the increase in age during the investigation. The complex growth rate (CGR) raised sharply after the 5th year, and amounted to the maximum at the 8th year when the LAI was 9.1.

Key words: P.gansuensis, growth analysis Biomass